Not sure why they classified this language as 'old English'. It's so far removed (from all perspectives including a fundamentally different grammatical system)

Not sure why they classified this language as 'old English'. It's so far removed (from all perspectives including a fundamentally different grammatical system) from modern or even early modern English, it's a completely different language altogether. I find "old English" to be a highly a misleading name as it implies continuity that simply isn't there in the same way it exists in say German.